The present invention relates to magnetic recording media, and more particularly relates to media such as recording disks for computer disk drive systems which include a soft magnetic layer comprising a multi-layer composite material.
Magnetic hard disk drives incorporating longitudinal recording heads are well known. However, as the magnetic volumes of recording bits decrease to support higher areal bit densities, conventional longitudinal media are subject to super paramagnetic instabilities which limit recording densities.
Perpendicular magnetic recording systems have been developed for use in computer hard disk drives. A typical perpendicular recording head includes a trailing main pole, a leading return pole magnetically coupled to the main pole, and an electrically conductive magnetizing coil surrounding the main pole. The bottom of the return pole has a surface area greatly exceeding the surface area of the tip of the main pole. Conventional perpendicular recording media typically include a hard magnetic recording upperlayer and a soft magnetic underlayer which provides a flux path from the trailing write pole to the leading return pole of the writer.
During recording operations, the perpendicular recording head is separated from the magnetic recording media by a distance known as the flying height. The magnetic recording media is moved past the recording head so that the recording head follows the tracks of the magnetic recording media, with the magnetic recording media first passing under the return pole and then passing under the main pole. Current is passed through the coil to create magnetic flux within the main pole. The magnetic flux passes from the main pole tip, through the hard magnetic recording track, into the soft underlayer, and across to the return pole.
When fabricating a perpendicular magnetic recording disk, one of the problems associated with the deposition of the soft underlayer is that the soft underlayer must be relatively thick, e.g., about 500 nm. This is not compatible with standard media sputtering processes where film thickness are typically in the range of about 50 nm. The incompatibility arises because of the timing issues in a standard media deposition processes where it takes only a few seconds to deposit a complete recording layer structure including buffers, seed layers and magnetic layers, while the time required to sputter a relatively thick soft underlayer film, e.g., 500 nm, would be on the order of minutes. This presents a production problem when depositing the soft underlayer and recording layer with conventional fabrication tools. The present invention has been developed in view of the foregoing.
An aspect of the present invention is to provide a magnetic recording disk including a magnetically soft layer and a magnetically hard recording layer. The magnetically soft layer includes a relatively thin layer of high saturation moment material and a relatively thick layer of low saturation moment material.
Another aspect of the present invention is to provide a method of making a soft magnetic layer of a magnetic recording disk. The method includes the steps of depositing a relatively thick layer of soft magnetic low saturation moment material on the disk, and depositing a relatively thin layer of high saturation moment soft magnetic material on the disk.
These and other aspects of the present invention will be more apparent from the following description.